The baby and O'Sullivan's wife, Sabrina, arrived back home and healthy on Thursday afternoon. The baby was 8 pounds, 11 ounces and 19 inches long.

"They are at home now relaxing, trying to catch up on some rest," O'Sullivan said.

He will also have to prepare for a transition to the bullpen. The Padres traded for Ian Kennedy, and he will take O'Sullivan's spot in the rotation.

With Tyson Ross in the rotation, O'Sullivan could serve as one of the long relievers in the Padres' bullpen along with Tim Stauffer.

"As with any reliever, you have to come to the park ready and have a bit of resiliency," said Padres manager Bud Black. "It'll be a little bit of a mind shift for him."

Jamal Collier is an associate reporter for MLB.com. Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.